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AddendumSince the completion of this systematic review of self-monitoring of blood glucose (SMBG) for patients with type 2 diabetes, one of the largest randomized control trials of SMBG was published in the British Medical Journal.1 This study provides an important contribution to the literature in that it is a well-designed trial that addresses many of the limitations of previous SMBG interventions, including sufficient power to detect clinically meaningful differences in HbA1c levels. In addition, it examined not only SMBG but also SMBG within a behavioral framework using psychological theory. Farmer and colleagues1 randomized 453 patients to 1 of 3 arms: a control where patients and their doctors received HbA1c readings prior to an appointment; an SMBG intervention that asked patients to monitor blood glucose 3 times a day, twice a week and talk to their doctor for interpretation; and an intense SMBG intervention that asked patients to monitor their glucose levels at the same rate and taught them skills for personal interpretation. All patients received a behavioral goal-setting intervention based on Leventhal's commonsense model of self-regulation. Although the intense self-monitoring group showed a 0.17% reduction in HbA1c, the between-group difference for HbA1c did not reach statistical significance.Although Farmer and colleagues1 should be commended for their well-thought-out and timely study, of concern is the discrepancy between HbA1c improvement found in this trial and the HbA1c improvement found in other trials. Of the 11 randomized control trials (RCTs) examined in this systematic review, only 1 found less improvement in HbA1c levels for the SMBG arm,2 with the majority showing at least 3 times the level of improvement. The results presented here suggest that patients who are in poor control are the ones who may benefit the most from SMBG. The mean baseline HbA1c level of 7.5% of the patients recruited by Farmer and colleagues1 may have limited the ability to detect improvement from monitoring. Consistent with this possibility, Farmer and colleagues' reporting of subgroups suggests that patients in their study who were in poorer control benefited the most from the SMBG intervention, as patients on oral medication had a greater reduction in HbA1c levels than those treated with diet alone (this effect was not statistically tested). Further analysis of mediating and moderating variables may provide clues as to why intensive intervention patients did not show significant improvements in HbA1c levels. Specifically, patients need to substitute objective readings (SMBG) for subjective cues to assess blood sugar levels. Participants in Farmer and colleagues' intensive intervention, however, were reporting significantly more subjective symptoms used to identify hypoglycemia episodes.1 As patients concerned about hypoglycemia have elevated glucose, intensive participants may have experienced conflict between subjective cues and objective indicators, accepted higher readings, and had the greatest difficulty with self-management based on objective readings. This is consistent with their less frequent use of meters. In addition, patients appear more likely to succeed in using SMBG to regulate diet and exercise if they monitor both before and 2 hours after a meal.3 In the paper by Farmer and colleagues, patients were described as monitoring either before or after a meal.4 It is unclear how patients could develop a behavioral regulatory system without specific feedback about their diet and exercise activities. Although the conclusion that SMBG may be effective in controlling HbA1c for patients with type 2 diabetes not treated with insulin is maintained here, the well-designed and adequately powered study by Farmer and colleagues1 highlights the difficulties both for conducting trials and for clinical practice. Attention to how (pre- and postaction), when (initially diagnosed), and for whom (poorly controlled) can maximize the possibility that SMBG can help the patients achieve effective blood sugar control. As patients develop a steady state of good diabetes control, they may use SMBG only as an occasional check. But as the patient's physiology changes, causing a deterioration of control, the individual should use SMBG to readjust his or her self-regulation. Recommendations to not use self-monitoring may have small ramifications in the short term, but as patients continue in maladaptive regulatory behaviors, the effects may be magnified. As such, trials should continue to examine the effect of SMBG on patients with type 2 diabetes not on insulin.
The Diabetes Educator, Vol. 33, No. 6,
1010-1011 (2007) Related articles in The Diabetes Educator:
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